1. Field of the Invention
The present invention relates to a motion detector for sensing a tremor movement produced by shooter's hand tremors, and also relates to an image capture device, an interchangeable lens and a camera system including such a motion detector.
2. Description of the Related Art
It is known that an image capture device will move due to a shooter's involuntary hand tremors and will also move when he or she intentionally changes the compositions for the purpose of panning the camera or panning shot, for example. To sense the movement of the former type (which is often called a “tremor movement”), an image stabilizer for detecting the tremor movement produced by shooter's unintentional hand tremors and an image capture device including such an image stabilizer have already been built in actual products.
However, an image capture device with such an image stabilizer will also sense and process the camera movement that has been intentionally produced by the shooter to change compositions for the purpose of panning the camera or panning shot, for example, as a kind of a tremor movement, thus sometimes making the shooter feel uncomfortable right after he or she has changed the compositions. More specifically, an image capture device senses relatively slight camera movement due to the shooter's hand tremors by amplifying them, and then uses it to stabilize the image. The magnitude of a movement produced to change the compositions is much greater than that of the tiny tremor movement. Nevertheless, the image capture device also attempts to process that movement by amplifying it. As a result, right after the change of compositions is done, the electric circuit for use to stabilize the image is too saturated to start eliminating the blurring caused by the tiny tremor movement immediately.
An image stabilizer designed to overcome such a problem is disclosed in Japanese Patent Application Laid-Open Publication No. 2002-99013. The image stabilizer includes means for extracting DC components from a motion detection signal and a memory to record the history of past DC components, and senses the start and end of change of compositions based on the difference between the motion detection signal and the DC components. If the DC components that were extracted when the compositions started to be changed are used when the change of compositions is done, the tremor movement can also be detected precisely enough even right after the compositions have been changed.
According to the technique disclosed in that patent document, however, the means for extracting DC components from a motion detection signal and the memory to record the history of past DC components are required. Addition of these pieces of extra hardware, however, would not just increase the manufacturing cost of a camera but also hinder reducing the size and weight or lowering the power dissipation thereof. That is why there is a growing demand for an image stabilizer that does not need any of those additional pieces of hardware.